The Universal Mobile Telecommunications System (UMTS) standards specified by the Third Generation Partnership Project (3GPP) define the Ciphering mechanisms carried out in the Radio Link Control (RLC) layer of UMTS equipment. The RLC layer is defined, for example, in “Universal Mobile Telecommunications System (UMTS); Radio Link Control (RLC) Protocol Specification (Release 11),” 3GPP TS 25.322, version 11.0.0, September, 2012, which is incorporated herein by reference. Ciphering in UMTS is defined, for example, in “3G Security; Security architecture (Release 11),” 3GPP TS 33.102, version 11.0.0, September, 2011, which is incorporated herein by reference.
U.S. Pat. No. 8,582,768, whose disclosure is incorporated herein by reference, describes a method in a receiver that includes receiving from a transmitter a sequence of communication packets. Carry data is encrypted with an encryption scheme. The encryption scheme depends on a counter value that is incremented independently by each of the transmitter and the receiver. Attempts are made to decrypt the data of a received packet multiple times using different, respective counter values, to produce multiple respective decrypted outputs. A decrypted output in which the data has been decrypted correctly is identified, the counter value is corrected, and the data of the received packet is recovered from the identified decrypted output.
The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application.